Position indicator

ABSTRACT

A position indicator includes a first electrode receiving an alternating current (AC) signal from a position detecting sensor and a second electrode transmitting an AC signal to the position detecting sensor. The position indicator includes: a tubular pen-shaped chassis; a central electrode provided such that one end protrudes outside of the chassis from an opening of the chassis, and formed of an electrically-conductive member forming a first one of the first and second electrodes; a peripheral electrode surrounding the central electrode and formed of an electrically-conductive member forming a second one of the first and second electrodes; and a shield member having a hollow part housing at least a part of the central electrode surrounded by the peripheral electrode. The shield member includes a tubular part electrically connected to ground and an insulating layer formed on an inner wall surface and an outer wall surface of the tubular part.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This disclosure relates to a position indicator used with a positiondetecting sensor.

2. Description of the Related Art

The following position indicator has been provided as a positionindicator used with a position detecting sensor in which positiondetection is performed. Specifically, the position indicator has aconfiguration of so-called full-duplex communication, in which a signalinput channel and a signal output channel independently exist, andthereby has a high affinity with the position detecting sensor.Furthermore, the position indicator has high general versatility and canensure predetermined waveform correlativity between an input signal andan output signal (refer to Japanese Patent No. 4683505 (Patent Document1)).

FIG. 10 is a diagram for explaining the conceptual configuration of aposition indicator 301 of this Patent Document 1 and the processingoperation thereof in a generalizing manner and shows a state in whichthe position indicator 301 is located over a plate surface of acapacitive position detecting sensor 302.

In the position indicator 301, a signal processing circuit 304 and abattery 305 that provides a supply voltage to the signal processingcircuit 304 are housed in a hollow part of a tubular chassis 303 thathas an opening on one end in the axial center direction and is formedinto a pen shape. The chassis 303 is formed by covering at least a partwhich an operator holds this position indicator in the outercircumferential surface of a tubular body formed of, e.g., an insulatingmaterial such as a synthetic resin by, e.g., an electrical conductorsuch as a metal.

As shown in a partially enlarged view of FIG. 11, the opening side ofthe chassis 303 of this position indicator 301 is formed as a taperedpart 303 a that gradually becomes thinner toward the tip, and aperipheral electrode 306 that is formed into a ring shape and is formedof a metal having electrical conductivity is attached to the outercircumferential side of the tapered part 303 a. Furthermore, a centralelectrode 307 is housed in the hollow part of the chassis 303 of theposition indicator 301 in a state in which a tip part 307 a of thecentral electrode 307 protrudes from the opening to the outside as shownin FIG. 11. The tip of the central electrode 307 is covered by anelastic protective member 307 b formed of electrically-conductiveelastic rubber or the like so that an indication input surface of theposition detecting sensor 302 may be prevented from being scratched anda contact area with the indication input surface may be made larger.

In this case, in the direction orthogonal to the axial center directionof the position indicator 301, the tapered part 303 a of the chassis 303intervenes between the peripheral electrode 306 and the centralelectrode 307. The peripheral electrode 306 and the central electrode307 are insulated from each other by this tapered part 303 a of thechassis 303. Moreover, in the direction orthogonal to the axial centerdirection of the position indicator 301, a shield member 308 foreffectively preventing electrical interference between the peripheralelectrode 306 and the central electrode 307 is provided between theperipheral electrode 306 and the central electrode 307. The shieldmember 308 is formed of a tubular conductor composed of anelectrically-conductive metal having an insulating layer 308 a formed onthe inner wall surface and the central electrode 307 is housed in thistubular conductor. Therefore, the central electrode 307 is configured tobe surrounded by the shield member 308 and the shield member isconnected to the ground (earth: the same hereinafter) to make acapacitive shield.

When this position indicator 301 is disposed over the position detectingsensor 302, as shown in FIG. 10, the peripheral electrode 306 is coupledto the position detecting sensor 302 via capacitance C1 and the centralelectrode 307 is also coupled to the position detecting sensor 302 viacapacitance C2.

Meanwhile, an alternating current (AC) signal flows in the positiondetecting sensor 302 and thus this AC signal is supplied as a currentsignal to the signal processing circuit 304 via the capacitance C1 andthe peripheral electrode 306. This signal processing circuit 304executes processing of intensifying a signal, such as amplifying aninput AC signal, and supplies an AC signal that is an output signal ofthe signal processing result to the central electrode 307. When theposition indicator 301 exists over the position detecting sensor 302,the central electrode 307 is coupled to the position detecting sensor302 via the capacitance C2 and thus the AC signal is returned from theposition indicator 301 to the position detecting sensor 302.

Because the intensified AC signal is returned from the positionindicator 301 to the position detecting sensor 302 in the above manner,the position detecting sensor 302 can detect the position indicated bythe position indicator 301 with high sensitivity.

In this case, when the voltage of the AC signal of the positiondetecting sensor 302 in the transmitting conductor is defined as V andthe voltage of the central electrode 307 of the position indicator 301is defined as e and capacitance between the peripheral electrode 306 andthe central electrode 307 is defined as C3 (see FIG. 10), a relationshipof

e≦C1/C3·V

is satisfied. Therefore, to increase the voltage e of the centralelectrode 307, it is advantageous that the capacitance C3 between theperipheral electrode 306 and the central electrode 307 is as low aspossible.

In the position indicator 301, the capacitance C3 between the peripheralelectrode 306 and the central electrode 307 is made low by interposingthe shield member 308 between the peripheral electrode 306 and thecentral electrode 307 to make the coupling between them as small aspossible. This can increase the voltage e and efficiently enhance thesensitivity.

As described in Patent Document 1, it is also possible for the positionindicator 301 to be configured to receive the AC signal from theposition detecting sensor 302 by the central electrode 307 and transmitthe AC signal resulting from the signal intensification by the signalprocessing circuit 304 from the peripheral electrode 306.

Recently, along with an increase in the preciseness of the indicatedposition in the position detecting sensor, demands for reduction in thethickness of the core body (central electrode) of the position indicatorand hence for reduction in the thickness of the position indicator areincreasing.

However, in the position indicator 301 of the above-described PatentDocument 1, an insulating part (tapered part 303 a of the chassis 303),a shield part (shield member 308), and an insulating part (insulatinglayer 308 a) need to be provided between the central electrode 307 andthe peripheral electrode 306 and it is difficult to satisfy the demandsfor the thickness reduction.

Furthermore, if a writing pressure being applied to the positionindicator can be detected in the position detecting sensor, e.g.,processing of changing the line width in line drawing by a user with useof the position indicator according to the writing pressure can beexecuted, which is convenient. Therefore, it is desirable for theposition indicator to be configured to include a writing pressuredetecting measure that detects the writing pressure applied to the corebody (central electrode) and transmit writing pressure informationdetected by this writing pressure detecting measure to the positiondetecting sensor.

To detect the writing pressure by such a writing pressure detectingmeasure, the writing pressure applied to the core body (centralelectrode) of the position indicator needs to be transmitted to thewriting pressure detecting measure. For this purpose, a configurationfor allowing the core body (central electrode) of the position indicatorto move in the axial center direction of the position indicator andsurely transmitting the writing pressure is necessary.

In this case, the position indicator needs to have a configuration toensure a predetermined thickness as the thickness of the core body inorder to surely transmit the writing pressure and allow the centralelectrode to move in the axial center direction of the positionindicator while having a structure to make the coupling between theperipheral electrode 306 and the central electrode 307 as small aspossible. Thus, it is more difficult to employ the configurationdesigned in consideration of thickness reduction.

SUMMARY OF THE INVENTION

An object of this disclosure is to provide a position indicator that cansolve the above problems.

To solve the above-described problems, in this disclosure,

a position indicator is provided that includes a first electrodereceiving an AC signal from a position detecting sensor and a secondelectrode transmitting an AC signal to the position detecting sensor andmakes position indication to the position detecting sensor. The positionindicator includes

a tubular chassis that is formed into a pen shape and has an opening onone end in an axial center direction,

a central electrode that is provided in the chassis such that one endprotrudes from the opening of the chassis to an outside, and is formedof a bar-shaped electrically-conductive member forming one of the firstelectrode and the second electrode,

a peripheral electrode that is provided to surround the centralelectrode on a side of the opening and is formed of anelectrically-conductive member forming another of the first electrodeand the second electrode, and

a shield member that is provided between the central electrode and theperipheral electrode and has a tubular part that is formed of anelectrically-conductive member and has a hollow part housing at least apart surrounded by the peripheral electrode in the central electrode,

wherein the shield member includes an insulating layer formed on aninner wall surface and an outer wall surface of the tubular partcorresponding to the part surrounded by the peripheral electrode in thecentral electrode, and the tubular part is electrically connected to theground.

In the position indicator according to this disclosure with theabove-described configuration, in the direction orthogonal to the axialcenter direction, the insulating layer is formed at least on the innerwall surface and the outer wall surface of the tubular part formed ofthe electrically-conductive member corresponding to the part surroundedby the peripheral electrode in the central electrode is interposedbetween the central electrode and the peripheral electrode. By thisshield member, the insulation and shield (mainly capacitive shield)between the central electrode and the peripheral electrode are realized.

Therefore, in the position indicator according to this disclosure, theconfiguration can be made in which only the shield member includes theinsulating layer formed on the inner wall surface and the outer wallsurface is disposed between the central electrode and the peripheralelectrode. Thus, thickness reduction of the position indicator can beeasily realized.

Furthermore, in this disclosure, it is more preferable to employ aconfiguration in which the tubular part of the shield member is composedof aluminum and the insulating layer is formed at least on the innerwall surface and the outer wall surface corresponding to the partsurrounded by the peripheral electrode in the central electrode byperforming alumite processing on the aluminum.

According to this disclosure, it is possible to make the configurationin which only the shield member including the insulating layer formed atleast on the inner wall surface and the outer wall surface correspondingto the part surrounded by the peripheral electrode in the centralelectrode is disposed between the central electrode and the peripheralelectrode. Thus, thickness reduction of the position indicator can beeasily realized.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of an example of an electronic apparatus with whicha position indicator according to an embodiment of this disclosure isused;

FIG. 2 is a diagram showing a configuration example of a positiondetecting sensor used with a position indicator according to anembodiment of this disclosure;

FIG. 3 is a partial sectional view of a configuration example of aposition indicator according to an embodiment of this disclosure;

FIG. 4 is a circuit diagram of a position indicator according to anembodiment of this disclosure;

FIG. 5 is a partial sectional view of a position indicator according toan embodiment of this disclosure;

FIG. 6 is a perspective view of exemplary components housed inside achassis of a position indicator according to an embodiment of thisdisclosure in an assembled state;

FIG. 7 is an exploded perspective view of the components shown in FIG.6;

FIG. 8 is a diagram showing the components shown in FIG. 7 in anassembled state;

FIG. 9 is a sectional view along line A-A in FIG. 6;

FIG. 10 is a circuit diagram of a conventional position indicator; and

FIG. 11 is a diagram showing part of a conventional position indicator.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An embodiment of the position indicator according to this disclosurewill be described below with reference to the drawings.

FIG. 1 shows one example of a tablet information terminal 200 as anexample of an electronic apparatus with which a position indicator 100according to an embodiment of this disclosure is used. In this example,the tablet information terminal 200 has a display screen 200D of adisplay device such as a liquid crystal display (LCD) and has acapacitive position detecting sensor 201 over the display screen 200D(on the front surface side).

[Configuration Example of Position Detecting Sensor 201]

The capacitive position detecting sensor 201 of this example is a mutualcapacitive position detecting sensor that has sensor electrodes composedof an input electrode and an output electrode and that detects a changein a coupling capacitance at a point touched by the position indicator100 as described below.

The capacitive position detecting sensor 201 of this example will bedescribed with reference to FIG. 2. Specifically, as shown in FIG. 2,the position detecting sensor 201 of this example is composed of asensor unit 210, a transmitting unit 211, and a receiving unit 212. Thesensor unit 210 includes plural, in this example 64, transmittingconductors 213Y₁, 213Y₂, . . . , 213Y₆₄ that extend along the horizontaldirection of the indication input surface (X-axis direction) and have astraight line shape and plural, in this example 64, receiving conductors214X₁, 214X₂, . . . , 214X₆₄ that are orthogonal to the transmittingconductors 213Y₁ to 213Y₆₄ and extend along the vertical direction ofthe indication input surface (Y-axis direction). The plural transmittingconductors 213Y₁ to 213Y₆₄ are disposed at equal intervals in the Y-axisdirection and are connected to the transmitting unit 211. The pluralreceiving conductors 214X₁ to 214X₆₄ are disposed at equal intervals inthe X-axis direction and are connected to the receiving unit 212.

In this specification, in a description of the transmitting conductors,they will be referred to as the transmitting conductors 213Y when thereis no need to discriminate them among the 64 transmitting conductors213Y₁ to 213Y₆₄. Similarly, in a description of the receivingconductors, they will be referred to as the receiving conductors 214Xwhen there is no need to discriminate them among the 64 receivingconductors 214X₁ to 214X₆₄.

The plural transmitting conductors 213Y are formed on the lower surfaceof a substrate for example. The plural receiving conductors 214X areformed on the upper surface of the substrate. Therefore, the pluraltransmitting conductors 213Y and the plural receiving conductors 214Xhave a placement relationship in which they are disposed opposed to eachother at a predetermined interval and are orthogonal to each other, andform plural intersections (cross-points). Furthermore, the transmittingconductor 213Y and the receiving conductor 214X are coupled to eachother via a predetermined capacitance at each cross-point.

The transmitting unit 211 supplies a predetermined AC signal to thetransmitting conductors 213Y. In this case, the transmitting unit 211may supply the same AC signal to the plural transmitting conductors213Y₁, 213Y₂, . . . , 213Y₆₄ while sequentially switching thetransmitting conductor one by one. Alternatively, the transmitting unit211 may simultaneously supply plural AC signals different from eachother to the plural transmitting conductors 213Y₁, 213Y₂, . . . ,213Y₆₄. Alternatively, the plural transmitting conductors 213Y₁, 213Y₂,. . . , 213Y₆₄ may be divided into plural groups and AC signalsdifferent on each group basis may be used.

The receiving unit 212 detects a signal component obtained bytransmission of the AC signal supplied to the transmitting conductor213Y to each of the receiving conductors 214X₁, 214X₂, . . . , 214X₆₄via the predetermined capacitance. If the coupling capacitance betweenthe transmitting conductor 213Y and the receiving conductor 214X isequal at all cross-points, a received signal at a predetermined level isdetected in the receiving unit 212 from all receiving conductors 214X₁,214X₂, . . . , 214X₆₄ in the sensor unit 210 when the position indicator100 is not disposed over the sensor unit 210.

On the other hand, when the position indicator 100 makes contact withthe sensor unit 210, the transmitting conductor 213Y and the receivingconductor 214X configuring the cross-point at the contact position andthe position indicator 100 are coupled to each other via capacitance.That is, the capacitance changes due to the position indicator 100, sothat the received signal level obtained from the receiving conductor214X of the cross-point at which the position indicator 100 existschanges compared with the received signal level of the othercross-points.

The receiving unit 212 detects the receiving conductor 214X in which thechange in the signal level of the received signal is caused among theplural receiving conductors 214X₁, 214X₂, . . . , 214X₆₄ to detect theposition of the position indicator 100. Then, a control unit (not shown)of the position detecting sensor 201 detects the cross-point with whichthe position indicator 100 is in contact by detecting the transmittingconductor 213Y to which the AC signal is being supplied from thetransmitting unit 211 and the receiving conductor 214X from which thechange in the signal level of the received signal is detected in thereceiving unit 212.

Also, when not the position indicator 100 but a finger gets close to ormakes contact with the sensor unit 210, the position detecting sensor201 can detect the cross-point the finger gets close to or contact with.In this case, part of the AC signal supplied to the transmittingconductor 213Y flows to the ground via the finger or the human body ofthe user and thus the signal level of the received signal of thereceiving conductor 214X configuring the cross-point at which the fingerexists changes. Therefore, by detecting this change in the signal levelof the received signal, the receiving unit 212 can detect the receivingconductor 214X configuring the cross-point at which the finger exists.

Also, in the case of the position indicator 100 having a pen shape(stylus shape), the position detecting sensor 201 can detect theindicated position in the sensor unit 210 similarly to the principle ofthe position detection of the finger. However, in the case of theposition indicator 100 having a pen shape, the contact area with theposition detecting sensor 201 is smaller than in the case of the finger.Thus, the coupling capacitance is lower and the detection sensitivity ofthe position detection in the position detecting sensor 201 is lower.

However, in the case of the position indicator 100 of this embodiment,the AC signal from the position detecting sensor 201 is received andprocessed by the signal processing circuit to intensify the signal andthen the resulting signal is returned to the position detecting sensor201 as described above. This enables the position detecting sensor 201to detect a contact position of the position indicator 100 with highsensitivity.

[Configuration Example of Position Indicator 100 of Embodiment]

<Outline of Configuration Example of Position Indicator 100>

An overview of the position indicator 100 according to an embodimentwill be described with reference to FIGS. 3 and 4. This positionindicator 100 includes a tubular chassis 1 composed of anelectrically-conductive material, specifically, e.g., steel special usestainless (SUS). At an opening of this chassis 1 on one end on a pen tipside of the pen shape thereof, a peripheral electrode 2 composed of anelectrically-conductive material, specifically, e.g., SUS, is providedwith the intermediary of an insulating sleeve 3. The insulating sleeve 3is to insulate the electrically-conductive chassis 1 from the peripheralelectrode 2 and is composed of, e.g., an insulating resin.

As shown in FIG. 4, inside the one end on the pen tip side of thechassis 1, a central electrode 5 is disposed in a state of being housedin a shield member 6. The shield member 6 is to shield the centralelectrode 5 and ensure insulation between the central electrode 5 andthe peripheral electrode 2. In this case, from the opening at one endpart on the pen tip side of the chassis 1, a tip part 5 a of the centralelectrode 5 protrudes to the outside and a tip part 6 a of the shieldmember 6 is exposed to the outside for example.

FIG. 3 is a diagram showing a state in which part of the tubular chassis1 of the position indicator 100 of this embodiment is represented as asection and part of the hollow part of the chassis 1 is exposed to theoutside. As shown in FIG. 3, the side opposite to the pen tip side ofthe chassis 1 is closed by a lid part 4 and a printed board 21 on whicha signal processing circuit and so forth (not shown in FIG. 3) aredisposed is housed in a hollow part 101 a of the tubular chassis 1.Furthermore, a battery 22 that provides a supply voltage to the signalprocessing circuit and so forth is housed between the printed board 21and the lid part 4. In this example, the lid part 4 is allowed to beremoved so that the battery 22 can be replaced.

FIG. 4 is a diagram showing a circuit example disposed on the printedboard 21 of the position indicator 100 of this embodiment and theelectrical connection relationship among the respective components inthe position indicator 100. As shown in FIG. 4, in the positionindicator 100 of this embodiment, a signal processing circuit 401, anintegrated circuit (IC) 402, and a wireless transmission circuit 403(i.e., a transmitter) are provided on the printed board 21. A powersupply circuit that provides a supply voltage from the voltage from thebattery 22 to these signal processing circuit 401, IC 402, and wirelesstransmission circuit 403 is also provided on the printed board 21although not shown in FIG. 4.

In this embodiment, the central electrode 5 is configured to beelectrically connected to the input terminal of the signal processingcircuit 401 and the output terminal of the signal processing circuit 401is configured to be electrically connected to the peripheral electrode2. In this example, the signal processing circuit 401 carries out phaseinversion on an AC signal (current signal) input via the centralelectrode 5 and then performs boosting (multiplication) by using atransformer, for example, to intensify the signal and supply theresulting signal to the peripheral electrode 2 as a voltage signal.

Therefore, the AC signal returned from the peripheral electrode 2 of theposition indicator 100 to the sensor unit 210 of the position detectingsensor 201 is a reverse-phase signal resulting from the intensificationof the AC signal supplied to the transmitting conductor 213Y. Thus, theposition indicator 100 functions to increase the change in the AC signalin the received signal of the receiving conductor 214X of the positiondetecting sensor 201. This enables the position detecting sensor 201 todetect the contact position of the position indicator 100 with highsensitivity.

In this embodiment, the chassis 1 of the position indicator 100 isformed of SUS as an electrically-conductive material and is connected toan earth conductor (not shown) formed on the printed board 21, on whichthe signal processing circuit 401 is provided. Therefore, the AC signalsupplied to the transmitting conductors 213Y in the position detectingsensor 201 flows to the ground via the chassis 1 of the positionindicator 100 and the human body of the user (see a dotted line in FIG.4), which allows further stabilization of the signal detectionoperation.

As shown in FIG. 4, in this embodiment, the shield member 6 has aconfiguration obtained by covering a tubular body 61 composed of anelectrically-conductive material by an insulating layer 62 across itswhole surface including the outer wall surface and inner wall surface.However, as described later, part of the shield member 6 is formed as apart at which the insulating layer 62 is not formed so that an outerwall surface 61 a of the tubular body 61 of the electrically-conductivematerial may be exposed at this part. This part at which the outer wallsurface 61 a is exposed is used as a terminal part for an electricalconnection to the earth conductor on the printed board 21. Electricalinsulation between the central electrode 5 and the peripheral electrode2 is realized by the insulating layer 62 of the shield member 6. Inaddition, a capacitive shield between the central electrode 5 and theperipheral electrode 2 is realized by the connection of the tubular body61 of the electrically-conductive material in the shield member 6 to theearth conductor.

Furthermore, in this embodiment, a writing pressure detecting unit 10that detects a pressure applied to the central electrode 5 forming thecore body, i.e., writing pressure, is provided in the hollow part 101 aof the chassis 1 of the position indicator 100 as shown in FIG. 4. Asdescribed later, this writing pressure detecting unit 10 has aconfiguration based on a variable-capacitance capacitor Cv that receivesthe writing pressure applied to the central electrode 5 via a pressuretransmitting member 7 and changes a capacitance of thevariable-capacitance capacitor Cv. As shown in FIG. 4, the centralelectrode 5 and the pressure transmitting member 7 are joined to eachother and are housed in a slidable state in the hollow part of thetubular body 61 of the shield member 6.

Both electrodes of the variable-capacitance capacitor Cv formed of thewriting pressure detecting unit 10 are connected to the IC 402. The IC402 calculates the writing pressure applied to the position indicator100 from the value of the capacitance of the variable-capacitancecapacitor Cv. Then, the IC 402 converts the calculated writing pressureto transmission data and transmits it to the position detecting sensor201 via the wireless transmission circuit 403. The wireless transmissioncircuit 403 is formed of, e.g., a near-distance wireless transmissionmeasure of the Bluetooth (registered trademark) standard or the like.The position detecting sensor 201 receives and decodes this transmissiondata of the writing pressure to detect the writing pressure applied tothe position indicator 100.

<Detailed Configuration Example of Major Part of Position Indicator 100>

FIG. 5 is a sectional view showing a detailed configuration example ofthe pen tip side of the position indicator 100 of this embodiment andcorresponds to the part that is not shown as the section in FIG. 3. Foreasier understanding, FIG. 5 shows a state obtained by cutting aperspective view of the pen tip side of the position indicator 100 by aplane including the central axis position of the tubular body formingthe chassis 1.

FIG. 6 is a diagram showing a component group housed in the hollow partof the tubular chassis 1 in an assembled state. FIG. 7 is an explodedperspective view of major components in the component group in this FIG.6. FIG. 8 is a diagram showing a state in which the major componentsshown in FIG. 7 are assembled and FIG. 9 is a sectional view along lineA-A in FIG. 6.

As shown in FIG. 5, the insulating sleeve 3 is formed into a truncatedcone shape that has an outer circumferential surface 3 a formed into atapered shape to gradually become thinner toward the pen tip side andhas a through-hole 3 b through which the shield member 6 to shield thecentral electrode 5 is inserted. The diameter of the pen tip side ofthis through-hole 3 b is set slightly larger for joining to theperipheral electrode 2. In addition, a screw part 3 c for screwing theperipheral electrode 2 is formed in the inner wall surface of the pentip side of the through-hole 3 b. Furthermore, the insulating sleeve 3has a protruding part 3 d that protrudes from the end surface of thelarger-diameter part on the side opposite to the pen tip side in theaxial center direction. This protruding part 3 d is press-fitted intothe opening end part of the pen tip side of the tubular chassis 1 andthereby the insulating sleeve 3 is fixed to the chassis 1. Symbol 3 edenotes a decorative ring and it is clamped and fixed between theinsulating sleeve 3 and the chassis 1 when the insulating sleeve 3 ispress-fitted and fixed to the chassis 1.

The peripheral electrode 2 is composed of SUS as an example of anelectrically-conductive material and is formed into a truncated coneshape that has an outer circumferential surface 2 a formed into atapered shape continuously with the outer circumferential surface 3 a ofthe insulating sleeve 3 and has a through-hole 2 b through which theshield member 6 in which the central electrode 5 is housed is inserted.Furthermore, a protruding part 2 c that protrudes in the axial centerdirection is provided on the side opposite to the pen tip side of theperipheral electrode 2. On this protruding part 2 c of the peripheralelectrode 2, a screw part 2 d screwed to the screw part 3 c of theinsulating sleeve 3 is formed.

The through-hole 2 b of the peripheral electrode 2 is formed such thatthe diameter of its part on the pen tip side is the minimum innerdiameter. As this minimum inner diameter, a diameter slightly largerthan the outer diameter of the part of the shield member 6 on the pentip side is selected. The inner diameter of the through-hole 2 b of theperipheral electrode 2 on the side of the screw part 2 d is set largerthan the minimum inner diameter. As described later, a terminal piece 9(see FIG. 6) for an electrical connection between the signal processingcircuit disposed on the printed board 21 and the peripheral electrode 2is allowed to be located in the space between this larger-inner-diameterpart of the through-hole 2 b and the shield member 6.

As shown in FIGS. 5, 7, and 8, the central electrode 5 includes a corebody 51 composed of an electrically-conductive material, specifically,e.g., a metal, whose diameter is set to, e.g., 1.9 mm. Furthermore, inthis embodiment, in the central electrode 5, about half of the core body51 on the pen tip side is covered by a protective member 52 composed ofan insulating material, specifically polyoxymethylene (POM) in thisexample. This part of the core body 51 covered by the protective member52 becomes a state in which the peripheral electrode 2 is located aroundthis part when being assembled as the position indicator 100. As shownin FIGS. 5 and 8, the core body 51 is formed such that its tip part hasa spherical shape and the protective member 52 is formed to cover thewhole of this spherical tip part of the core body 51 and forms the tippart 5 a of the central electrode 5. This protective member 52 has rolesin preventing scratching of the indication input surface of the positiondetecting sensor 201 and increasing the contact area with the indicationinput surface. Furthermore, particularly in this embodiment, theprotective member 52 has a role in strengthening insulation from theshield member 6 and the peripheral electrode 2.

In this embodiment, the tubular body 61 composed of anelectrically-conductive material forming the shield member 6 is composedof alumite-processed aluminum. Furthermore, as shown in FIGS. 5 and 8,the insulating layer 62 is formed of an alumite coat formed to cover thewhole surface of the tubular body 61 including the outer wall surface 61a and an inner wall surface 61 b.

However, the alumite processing of the tubular body 61 is performed suchthat, at a terminal part 63, the insulating layer 62 is not formed andthe outer wall surface 61 a of the tubular body 61 composed of theelectrically-conductive material is exposed as shown in FIGS. 6 and 7.The terminal part 63 of the tubular body 61 is electrically connected tothe earth conductor (ground) of the printed board 21 and an electricfield shield of the central electrode 5 is formed by the tubular body61. This terminal part 63 can be formed by masking the correspondingpart when alumite processing of the tubular body 61 is performed forexample. Alternatively, after the alumite processing, the alumite coatat the terminal part 63 may be removed to expose the outer wall surface61 a of the tubular body 61.

In this embodiment, as described by using FIG. 4, in the hollow part ofthe tubular body 61 of the shield member 6, the central electrode 5 andthe pressure transmitting member 7 joined to each other are housedmovably in this hollow part in the axial center direction of the centralelectrode 5. As the pressure transmitting member 7, a member having alarger diameter than the central electrode 5 is used.

For this reason, as shown in FIGS. 5 and 8, the tubular body 61 of theshield member 6 is configured to have a smaller-diameter part 64 havingsuch an inner diameter as to house the central electrode 5 movably inthe axial center direction mainly on the pen tip side and alarger-diameter part 65 having such an inner diameter as to house thepressure transmitting member 7 movably in the axial center direction onthe opposite side to the pen tip side.

As the inner diameter of the hollow part of the smaller-diameter part64, a diameter slightly larger than the outer diameter of the centralelectrode 5 (diameter of the part where the protective member 52 isformed on the core body 51) is selected. Furthermore, as the innerdiameter of the larger-diameter part 65, a diameter slightly larger thanthe maximum diameter of the pressure transmitting member is selected.Therefore, in the hollow part of the tubular body 61, a step part 66 isformed at the part at which the change from the smaller-diameter part 64to the larger-diameter part 65 is made. Furthermore, also on the outercircumferential side surface of the tubular body 61, a step part 67 isformed at the part at which the change from the smaller-diameter part 64to the larger-diameter part 65 is made.

The pressure transmitting member 7 is formed of an insulating material,specifically a resin in this example. As shown in FIGS. 5, 7, and 8, thepressure transmitting member 7 has a core body fitting part 71 intowhich an end part 51 b of the core body 51 of the central electrode 5 isfitted and a protruding part 72 fitted into the writing pressuredetecting unit 10. The core body fitting part 71 of the pressuretransmitting member 7 is configured by forming a recess 71 a into whichthe end part 51 b of the core body 51 of the central electrode 5 isinserted in a circular columnar member. As shown in FIG. 7, at part ofthe side circumferential surface of this core body fitting part 71, aslit 71 b obtained by notching the sidewall of the recess 71 a in theaxial center direction from the opening side to the bottom part isformed. As shown in FIGS. 5 and 8, the protruding part 72 of thepressure transmitting member 7 is joined to the writing pressuredetecting unit 10 for transmitting a writing pressure thereto.

As shown in FIGS. 7 and 8, in the recess 71 a, a terminal piece 73 foran electrical connection between the central electrode 5 and the signalprocessing circuit 401 of the printed board 21 is disposed. Thisterminal piece 73 is formed of a metal plate and, as shown in FIGS. 7and 8, has a pair of first terminal pieces 73 a that are disposedopposed to each other in a direction orthogonal to the axial centerdirection and are formed to extend along the axial center direction inthe recess 71 a and a second terminal piece 73 b disposed to protrude ina direction orthogonal to the outer circumferential side surface of thecore body fitting part 71 of the pressure transmitting member 7 throughthe slit 71 b. The pair of first terminal pieces 73 a are formedelastically displaceably in the direction orthogonal to the axial centerdirection and are disposed such that the interval thereof is the same asor somewhat smaller than the diameter of the core body 51.

The core body 51 of the central electrode 5 is joined to the pressuretransmitting member 7 by insertion (press-fitting) of its end part 51 binto the recess 71 a of the core body fitting part 71 of the pressuretransmitting member 7, and a writing pressure applied to the core body51 is transmitted to the writing pressure detecting unit 10 to bedescribed later via the pressure transmitting member 7. Specifically,the end part 51 b of the core body 51 of the central electrode 5 ispress-fitted into between the pair of first terminal pieces 73 a in therecess 71 a of the core body fitting part 71 against the elasticdisplacement force of them. Along with this, the core body 51 of thecentral electrode 5 is elastically clamped by the pair of terminalpieces 73 a as shown in FIG. 8. Therefore, the central electrode 5 islocked to the pressure transmitting member 7 and is set to a state inwhich the locking to the pressure transmitting member 7 is not releasedunless the central electrode 5 is pulled out by a predetermined force.

The unit obtained by the joining of the central electrode 5 and thepressure transmitting member 7 in the above manner is housed movably inthe axial center direction in the tubular body 61 of the shield member6. The core body fitting part 71 of the pressure transmitting member 7engages with the step part 66 of the hollow part of the tubular body 61of the shield member 6, which prevents the central electrode 5 and thepressure transmitting member 7 from dropping off to the pen tip side.However, when a force is applied to pull out only the central electrode5, the elastic clamping of the end part 51 b of the core body 51 by thefirst terminal pieces 73 a is released and the central electrode 5 canbe pulled out from the pressure transmitting member 7. That is, aconfiguration enabling replacement of the central electrode 5 is made.

Next, the writing pressure detecting unit 10 will be described below. Asthe writing pressure detecting unit 10 of this example, a writingpressure detecting measure having a known configuration described inpatent document, Japanese Patent Laid-Open No. 2011-186803 is used forexample. The writing pressure detecting unit 10 configures avariable-capacitance capacitor whose capacitance changes according tothe writing pressure applied to the central electrode 5.

As shown in FIGS. 5 and 8, the writing pressure detecting unit 10 ofthis example is formed by housing plural components, a dielectric 12, anelectrically-conductive member 13, an elastic member 14, a holdingmember 15, and a terminal member 16, in a housing member 11 composed ofan insulating material, specifically, e.g., a resin. The terminal member16 forms a first electrode of the variable-capacitance capacitorconfiguring the writing pressure detecting unit 10. Furthermore, theelectrically-conductive member 13 and the elastic member 14 areelectrically connected to each other and form a second electrode of thevariable-capacitance capacitor.

The housing member 11 is formed of a tubular body having a hollow partand has a configuration to arrange the holding member 15, the elasticmember 14, the electrically-conductive member 13, the dielectric 12, andthe terminal member 16 in the axial center direction and house them inthe hollow part. The dielectric 12 and the terminal member 16 are fixedso as not to move in the axial center direction relative to the housingmember 11.

The holding member 15 is provided movably in the axial center directionrelative to the housing member 11. At the end surface of this holdingmember 15 on the pen tip side, a recess 15 a into which the protrudingpart 72 of the pressure transmitting member 7 is fitted is made. By thepress-fitting of the protruding part 72 of the pressure transmittingmember 7 into this recess 15 a of the holding member 15, the whole ofthe central electrode 5, the pressure transmitting member 7, and theholding member 15 is allowed to move in the axial center directionaccording to the writing pressure applied to the central electrode 5.

At the end surface of the holding member 15 on the opposite side to theend surface at which the recess 15 a is formed, theelectrically-conductive member 13 is joined and held. Thiselectrically-conductive member 13 is formed of a member that haselectrical conductivity and is elastically deformable, specifically,e.g., an elastic member such as a silicone conductive rubber or apressure conductive rubber. The elastic member 14 is formed of, e.g., acoil spring having electrical conductivity. The elastic member 14 has awinding part having elasticity and a terminal piece (not shown) at oneend part of this winding part, and has a connecting part 14 a at theother end part of the winding part.

The elastic member 14 is combined to surround theelectrically-conductive member 13 held by the holding member 15 by itswinding part. At this time, an end surface of theelectrically-conductive member 13 makes contact with the connecting part14 a of the elastic member 14 having electrical conductivity and becomesin a state of being electrically connected thereto. The terminal piece(not shown) at the end part on the opposite side to the connecting part14 a of the elastic member 14 is configured to be soldered to anelectrically-conductive pattern of the printed board 21.

The terminal member 16 is configured to be electrically connected to anelectrically-conductive pattern of the printed board 21 (this connectionis not shown).

In the writing pressure detecting unit 10 configured as above, when awriting pressure is applied to the central electrode 5, this writingpressure is transmitted to the holding member 15 of the writing pressuredetecting unit 10 via the pressure transmitting member 7 and the holdingmember 15 moves the electrically-conductive member 13 toward thedielectric 12 according to the applied writing pressure. Along withthis, an end part of the electrically-conductive member 13 abuts againstthe dielectric 12 and the contact area with the electrically-conductivemember 13 changes according to the applied writing pressure. Thus, thecapacitance of the variable-capacitance capacitor formed between thefirst electrode and the second electrode is changed according to theapplied writing pressure.

Then, as described above, the position indicator 100 of this embodimentdetects, by the IC 402, the writing pressure applied to the positionindicator 100 from the capacitance of the variable-capacitance capacitorconfiguring the writing pressure detecting unit 10 and transmitsinformation on the detected writing pressure through the wirelesstransmission circuit 403.

[Connection Between Central Electrode 5 and Input Terminal of SignalProcessing Circuit 401]

The terminal piece 73 disposed in the pressure transmitting member 7 isa member for electrically connecting the central electrode 5 to thesignal processing circuit disposed on the printed board 21. The end part51 b of the core body 51 of the central electrode 5 elastically makescontact with the first terminal pieces 73 a and thereby the centralelectrode 5 is electrically connected to the terminal piece 73.

The length of the second terminal piece 73 b of the terminal piece 73 isset to such a length that its tip protrudes to the outside of thehousing member 11 of the writing pressure detecting unit 10 as shown inFIGS. 7 and 8. Furthermore, as shown in FIGS. 7 and 9, a notch having aV-shape or a U-shape is made at the tip of this second terminal piece 73b of the terminal piece 73.

To this V-shaped or U-shaped notch at the tip of the second terminalpiece 73 b, one end of a connecting line 23 formed of, e.g., a copperline is soldered as shown in FIGS. 8 and 9. The other end of thisconnecting line 23 is connected by soldering or the like to a conductorpattern to which an input terminal of the signal processing circuit 401provided on the printed board 21 is connected, although not shown in thediagram.

Because the second terminal piece 73 b of the terminal piece 73 housedin the pressure transmitting member 7 is configured to protrude to theoutside of the housing member 11 of the writing pressure detecting unit10, the connecting line 23 is disposed at such a position as to connectthe second terminal piece 73 b of the terminal piece 73 to the printedboard 21 while bypassing the whole of the writing pressure detectingunit 10 interposed between the printed board 21 and the pressuretransmitting member 7.

[Connection Between Tubular Body 61 of Shield Member 6 and EarthConductor]

Next, a configuration for the connection between the tubular body 61 ofthe shield member 6 and the earth conductor of the printed board 21 willbe described. Specifically, also as described above, the tubular body 61of the electrically-conductive material configuring the shield member 6needs to be electrically connected to the earth conductor of the printedboard 21. The earth conductor of the printed board 21 is electricallyconnected to the chassis 1. Therefore, when a user holds the chassis andoperates the position indicator 100, the earth conductor is connected tothe earth (ground) via the human body and provides a favorable shieldeffect.

As shown in FIGS. 5, 6, and 9, in this embodiment, the shield member 6and the writing pressure detecting unit 10 are disposed in a holder 30.This holder 30 has a so-called dugout-like shape like a shape obtainedby cutting the tubular body 61 by a plane along the axial centerdirection thereof. The part of the holder 30 to house the shield member6 has a recess shape corresponding to the outer shape of the shieldmember 6. Furthermore, the part to house the writing pressure detectingunit 10 has a recess shape corresponding to the outer shape of thehousing member 11 of the writing pressure detecting unit.

As shown in FIGS. 5 and 6, in this example, the step part 67 formed onthe side of the outer wall surface 61 a of the tubular body 61 of theshield member 6 engages with a step part 31 formed in the holder 30 andthereby the shield member 6 is prevented from moving in the axial centerdirection in the holder 30. Furthermore, the writing pressure detectingunit 10 is prevented from moving in the axial center direction by thecombination of the recess corresponding to the outer shape of thewriting pressure detecting unit 10 and the preventing the shield member6 from moving in the axial center direction. Furthermore, as shown inFIG. 5, the holder 30 abuts against the insulating sleeve 3 to berestricted from moving toward the opening side of the chassis 1 on thepen tip side. In addition, the printed board 21 joined and fixed to thisholder 30 is fixed by the lid part 4 with the intermediary of thehousing part of the battery 22 and thereby the holder 30 is alsorestricted from moving toward the lid part 4.

As shown in FIG. 6, in this example, at one end of the printed board 21in the longitudinal direction, arm parts 21 a and 21 b extending alongthe longitudinal direction of the printed board 21 are formed from bothend parts of the printed board 21 in a direction orthogonal to thelongitudinal direction. The arm parts 21 a and 21 b of this printedboard 21 are joined to the opening end surface of the part at which thewriting pressure detecting unit 10 is housed in the holder 30 andthereby the printed board 21 is fixed to the holder 30.

In this case, although not shown in the diagram, a conductor pattern toconnect to the output terminal of the signal processing circuit 401disposed on the printed board 21 is formed on the arm part 21 a and aconductor pattern to connect to the earth conductor of the printed board21 is formed on the arm part 21 b.

In this embodiment, as shown in FIGS. 5, 6, 8, and 9, a ring terminalpiece 8 shown in FIG. 7 is provided between the pressure transmittingmember 7 and the housing member 11 of the writing pressure detectingunit 10. In this case, the ring terminal piece 8 is formed to havesubstantially the same size and shape as an end surface of the tubularhousing member 11. Furthermore, the protruding part 72 of the pressuretransmitting member 7 is inserted through a ring space 8 a of the ringterminal piece 8 and the ring terminal piece 8 is clamped by a step partformed between the core body fitting part 71 and the protruding part 72and the end surface of the housing member 11 of the writing pressuredetecting unit 10.

In this ring terminal piece 8, connection protrusions 8 b and 8 c areformed at positions corresponding to the terminal parts 63, at which theouter wall surface 61 a of the tubular body 61 provided in the shieldmember 6 is exposed. The terminal parts 63 of the tubular body 61 areformed at two positions that are opposed to each other and are separateby an angular interval of 180 degrees. The connection protrusions 8 band 8 c are formed corresponding to these two terminal parts 63.Furthermore, in the ring terminal piece 8, a connection protrusion 8 dto connect to the electrically-conductive pattern connected to the earthconductor formed on the arm part 21 b of the printed board 21 is alsoformed.

As shown in FIGS. 6 and 9, the connection protrusions 8 b and 8 c of thering terminal piece 8 are each soldered to the outer wall surface 61 aof the tubular body 61 exposed at the terminal part 63 of the shieldmember 6 in a state of being brought into contact with the outer wallsurface 61 a. Furthermore, as shown in FIGS. 6 and 9, the connectionprotrusion 8 d of the ring terminal piece 8 is soldered in a state ofbeing connected to the earth conductor formed on the arm part 21 b ofthe printed board 21. By the above configuration, the tubular body 61composed of an electrically-conductive material in the shield member 6is connected to the earth conductor of the printed board 21 and anelectric field shield is realized.

[Connection Between Peripheral Electrode 2 and Output Terminal of SignalProcessing Circuit 401]

Next, a configuration for an electrical connection between theperipheral electrode 2 and the output terminal of the signal processingcircuit 401 of the printed board 21 will be described.

Specifically, in this embodiment, as shown in FIG. 7, the terminal piece9 for the peripheral electrode 2 is prepared by, e.g., a metal platehaving elasticity as a component having a shape allowing elasticdisplacement in its plate thickness direction. On one end side of thisterminal piece 9 for the peripheral electrode 2 in the longitudinaldirection, a connection protrusion 9 a connected to the conductorpattern connected to the output terminal of the signal processingcircuit 401 formed on the arm part 21 a of the printed board 21 isformed. On the other hand, a connection end part 9 b that elasticallymakes contact with the inner wall surface of the peripheral electrode 2is formed on the other end side of this terminal piece 9 for theperipheral electrode 2 in the longitudinal direction.

This terminal piece 9 for the peripheral electrode 2 is fixed to theholder 30 by fitting of the side of the connection protrusion 9 a into apocket part (not shown) formed in the holder 30. As shown in FIG. 6,this terminal piece 9 for the peripheral electrode 2 is fixed along theouter wall surface of the housing recess for the shield member 6 in theholder 30, with its longitudinal direction set to the same direction asthe axial center direction. Therefore, when the peripheral electrode 2is screwed to the insulating sleeve 3, the inner wall surface of theperipheral electrode 2 elastically makes contact with the connection endpart 9 b of the terminal piece 9 and is electrically connected thereto.

[Isolation Between Connecting Line 23 and Terminal Piece 9 forPeripheral Electrode 2]

In this embodiment, the connecting line 23 for the electrical connectionbetween the central electrode 5 and the input terminal of the signalprocessing circuit 401 of the printed board 21 and the terminal piece 9for the electrical connection between the peripheral electrode 2 and theoutput terminal of the signal processing circuit of the printed board 21form a signal line for a received signal and a signal line for atransmission signal, respectively. The connecting line 23 and theterminal piece 9 are both disposed along the axial center direction insuch a manner as to straddle the writing pressure detecting unit 10. Forthis reason, there is a fear that the transmission signal and thereceived signal interfere with each other and the position indicator 100becomes incapable of stably operating.

In view of this point, in this embodiment, the occurrence of theinterference between the transmission signal and the received signal isprevented as described below.

First, in the hollow part of the chassis 1 of the position indicator100, the placement position of the connecting line 23 as the signal lineof the received signal and the placement position of the terminal piece9 forming the signal line of the transmission signal are set atpositions separate from each other by 180 degrees, which are positionsseparate from each other at the highest degree, in the circumferentialdirection of the hollow part of the chassis 1.

Second, in this embodiment, the connecting line 23 as the signal line ofthe received signal is isolated from the terminal piece 9 and isshielded (electromagnetically shielded). Specifically, as shown in FIGS.5 and 9, the connecting line 23 is covered by a copper tape 40configured by forming an insulating coating layer 42 on one surface of arolled copper foil 41. At this time, the copper tape 40 is disposedalong the writing pressure detecting unit 10, with the insulatingcoating layer 42 located on the side of the connecting line 23. As shownin FIG. 9, in this embodiment, the connecting line 23 is disposed in agroove 32 formed at part of the circumferential side surface of theholder 30 in such a manner as to bypass the writing pressure detectingunit 10 housed and held in the holder 30.

Furthermore, in this embodiment, one end 41 a of the rolled copper foil41 is soldered to the arm part 21 b of the printed board 21 fixed to theholder 30 and the copper tape 40 is connected to the earth conductorformed on the arm part 21 b. In this case, the length of the copper tape40 in the circumferential direction is set to such a length as to coveran angular range of about 180 degrees from the arm part 21 b of theprinted board 21 to a position immediately before the placement positionof the terminal piece 9 as shown in FIG. 9. Furthermore, the rangecovered by the copper tape 40 in the axial center direction includes thewhole of the housing part for the writing pressure detecting unit 10 inthe holder 30 in the axial center direction and reaches the base part ofthe arm part 21 b of the printed board 21.

By the above configuration, the signal line of the received signal bythe connecting line 23 to connect the central electrode 5 and the inputterminal of the signal processing circuit 401 and the signal line of thetransmission signal by the terminal piece 9 to connect the peripheralelectrode 2 and the output terminal of the signal processing circuit 401are electrically isolated from each other by the shield based on thecopper tape 40, so that the interference between the transmission signaland the received signal is suppressed.

Effects of Embodiment

In the above manner, in the position indicator 100 of this embodiment,in the shield member 6, the insulating layer 62 formed of an alumitecoat is formed across the whole of the tubular body 61 including theouter wall surface 61 a and the inner wall surface 61 b by performingalumite processing on the whole of the tubular body 61 (excluding theterminal part 63) composed of aluminum. Furthermore, the aluminum as anelectrically-conductive material is connected to the earth conductor ofthe printed board 21 at the terminal part 63 and thereby an electricfield shield is realized.

Therefore, according to this embodiment, the insulation and shieldbetween the central electrode 5 and the peripheral electrode 2 can berealized by only the shield member 6 and the thickness of the pen tipside can be reduced. In addition, the central electrode 5 can beconfigured to be covered by the whole of the shield member 6 and thusthe thickness of the central electrode 5 can be further reduced.

Moreover, in this embodiment, the protective member 52 is provided atthe part surrounded by the peripheral electrode 2 in the core body 51forming the central electrode 5 and thus the insulation between thecentral electrode 5 and the peripheral electrode 2 is furtherstrengthened.

Furthermore, in this embodiment, the central electrode 5 itself is notused to transmit a pressure to the writing pressure detecting unit 10and the pressure is transmitted via the pressure transmitting member 7.Thus, although the thickness of the central electrode 5 is reduced, aneffect that a writing pressure can be surely transmitted to the writingpressure detecting unit 10 is provided by the pressure transmittingmember 7.

In addition, according to this embodiment, the central electrode 5 isallowed to be inserted and removed into and from the pressuretransmitting member 7 and thus there is also an effect that the centralelectrode 5 can be replaced.

Moreover, in this embodiment, the signal line of the received signal bythe connecting line 23 to connect the central electrode 5 and the inputterminal of the signal processing circuit 401 and the signal line of thetransmission signal by the terminal piece 9 to connect the peripheralelectrode 2 and the output terminal of the signal processing circuit 401are disposed in the hollow part of the chassis 1. However, theconnecting line 23 is shielded by the copper tape 40, which provides aneffect that the interference between the transmission signal and thereceived signal is suppressed.

Other Embodiments or Modification Examples

In the above-described embodiment, the central electrode 5 is used as areceiving electrode for a signal from the position detecting sensor andthe peripheral electrode is used as a transmitting electrode to transmita signal to the position detecting sensor. However, as described also atthe beginning, it is also possible to make a configuration to use thecentral electrode as the transmitting electrode and use the peripheralelectrode as the receiving electrode.

In the above-described embodiment, in the shield member 6, theinsulating layer 62 is formed to cover the whole surface of the tubularbody 61 composed of an electrically-conductive material except theterminal part for an electrical connection. However, because it isenough that insulation between the peripheral electrode 2 and thecentral electrode 5 can be ensured, it suffices for the insulating layer62 on the tubular body 61 of the shield member 6 to be formed at leastin a region corresponding to the region in which the peripheralelectrode 2 surrounds the central electrode 5.

Similarly, it also suffices for the protective member 52, which isformed to cover the tip part side of the core body 51 of the centralelectrode 5 and is composed of an insulating material, to be formed atleast in a region range corresponding to the region in which theperipheral electrode 2 surrounds the central electrode 5.

Furthermore, in the above-described embodiment, in the shield member 6,the tubular body 61 is formed by aluminum and the insulating layer 62 isformed by performing alumite processing. However, the shield member 6 isnot limited to this configuration and may be so configured that thewhole of the tubular body 61 of an electrically-conductive material iscovered by an insulating layer except the terminal part 63.

Moreover, in the above-described embodiment, in the writing pressuredetecting unit 10, the variable-capacitance capacitor whose capacitancechanges according to the writing pressure is used by interposing adielectric between the first electrode and the second electrode andallowing one of the first electrode and the second electrode to move inthe axial center direction according to the writing pressure. However,the writing pressure detecting unit 10 is not limited to thisconfiguration. For example, it is also possible to configure the writingpressure detecting unit 10 by using a semiconductor element that allowscapacitance to change according to the writing pressure like onedisclosed in Japanese Patent Laid-Open No. 2013-161307. Furthermore, thewriting pressure detecting unit may be configured by using a structureor an element that allows not capacitance but an inductance value or aresistance value to change according to the writing pressure.

It is to be noted that the embodiment of the present disclosure is notlimited to the foregoing embodiments, and that various changes can bemade without departing from the spirit of the present disclosure.

What is claimed is:
 1. A position indicator that indicates a position toa position detecting sensor, the position indicator comprising: apen-shaped tubular chassis having an opening at a distal end in an axialcenter direction; a central electrode having an elongated shapeincluding a distal end and provided in the chassis such that the distalend of the central electrode protrudes outside of the chassis from theopening of the chassis; a peripheral electrode that surrounds thecentral electrode; and a shield provided between the central electrodeand the peripheral electrode, wherein the shield includes anelectrically-conductive tubular part and a hollow part and the hollowpart houses the central electrode so as to be moveable in the axialcenter direction.
 2. The position indicator according to claim 1,wherein the shield includes insulating layers formed on an inner wallsurface and an outer wall surface of the tubular part adjacent to a partof the central electrode that is surrounded by the peripheral electrode,and the tubular part is electrically connected to a ground conductor. 3.The position indicator according to claim 1, wherein at least the distalend of the central electrode protruding outside of the chassis iscovered by a non-electrically-conductive material having a frictionalresistance that is lower than a frictional resistance of the centralelectrode.
 4. The position indicator according to claim 1, furthercomprising: a writing pressure detector provided in the chassis andconfigured to detect a pressure applied to the distal end of the centralelectrode.
 5. The position indicator according to claim 4, wherein thewriting pressure detector includes a variable-capacitance capacitor thatincludes two electrodes opposed to each other in the axial centerdirection of the chassis with a dielectric interposed between the twoelectrodes, and a capacitance between the two electrodes changesaccording to the pressure applied to the distal end of the centralelectrode protruding from the opening of the chassis.
 6. The positionindicator according to claim 4, further comprising: a pressuretransmitting member coupled to the proximal end of the centralelectrode, the pressure transmitting member, in operation, transmits thepressure applied to the central electrode to the writing pressuredetector, wherein the pressure transmitting member includes a terminalpiece that electrically connects the central electrode to circuitry. 7.The position indicator according to claim 6, wherein the pressuretransmitting member is housed movably in the hollow part of the shield.8. The position indicator according to claim 6, further comprising: aterminal member that is disposed between the shield and the writingpressure detector and that electrically connects the tubular part of theshield to a ground conductor of the circuitry.
 9. The position indicatoraccording to claim 4, further comprising: a transmitter that, inoperation, transmits data corresponding to the pressure detected by thewriting pressure detector to the position detecting sensor.
 10. Theposition indicator according to claim 1, wherein a signal transmittedvia the peripheral electrode has a predefined correlation with a signalreceived via the central electrode.
 11. The position indicator accordingto claim 1, further comprising: a printed board including circuitrydisposed in the chassis; and a holding part disposed in the chassis andcomposed of an insulating material, wherein the shield is disposed inthe holding part and the holding part is fixed to the printed board. 12.The position indicator according to claim 11, further comprising: aplate-shaped terminal piece formed of an electrically-conductivematerial and having a distal end and a proximal end, wherein the distalend of the plate-shaped terminal piece is fixed to the holding part andis electrically connected to the circuitry on the printed board, and theproximal end of the plate-shaped terminal piece is elasticallydisplaceable in a direction intersecting the axial center direction andis electrically connected to the peripheral electrode.